Cooling system for electric vehicles

Abstract

To provide a cooling system for electric vehicle that can achieve both of pump load reduction and drive unit cooling improvement.SOLUTION: A cooling system 40 is a cooling system for electric vehicle, which is equipped with a drive unit 60 located in the front of a vehicle 1 and a battery charger 8 located on a rear side with respect to the drive unit 60, comprises: a cooling liquid circuit 42 which is connected to the drive unit 60 and the battery charger 8, and has a sixth path 42f bypassing the battery charger 8; and a control device 10 which controls circulation of a cooling liquid to the cooling liquid circuit 42. The control device 10 feeds the cooling liquid to the sixth path 42f when the battery charger 8 is not operating and a temperature of the drive unit 60 is less than a prescribed temperature, and feeds the cooling liquid to the drive unit 60 after feeding the same to the battery charger 8 when the battery charger 8 is not operating and the temperature of the drive unit 60 is the prescribed temperature or more.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] This disclosure relates to a cooling system for electric vehicles. [Background technology]

[0002] In cooling systems for electric vehicles (EVs) and plug-in hybrid vehicles (PHVs), a system is known in which the coolant discharged from the radiator is circulated in the following order: DC / DC converter, inverter, charger, converter, generator, and drive motor (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-30810 [Overview of the project] [Problems that the invention aims to solve]

[0004] By the way, in the technology described in Patent Document 1, of the above-mentioned electrical devices, the electrical devices other than the charger, i.e., the drive unit, are located in the motor room at the front of the vehicle, while the charger is located at the rear of the vehicle.

[0005] While the charger requires cooling during operation, it does not require cooling when not in operation. Therefore, from the perspective of reducing the pump load, it is conceivable to bypass the circulation of coolant to the charger when not in operation. On the other hand, under conditions where the coolant temperature tends to rise, such as during high torque, the cooling of the drive unit needs to be strengthened compared to normal driving. Thus, from the perspective of achieving both reduced pump load and improved drive unit cooling, there is room for improvement in the conventional cooling system.

[0006] Therefore, this disclosure aims to provide a cooling system for electric vehicles that can achieve both reduced pump load and improved cooling of the drive unit. [Means for solving the problem]

[0007] To solve the above problems, one embodiment of a cooling system for an electric vehicle disclosed herein is a cooling system for an electric vehicle comprising a drive unit located in front of the vehicle and a charger located behind the drive unit, comprising: a coolant circuit connected to the drive unit and the charger and having a bypass path that bypasses the charger; a pump provided on the coolant circuit for supplying coolant to the coolant circuit; a heat exchanger provided on the coolant circuit for cooling the coolant; a temperature detection means provided on the drive unit for detecting the temperature of the drive unit; and a control device that controls the circulation of the coolant to the coolant circuit based on the temperature of the drive unit detected by the temperature detection means. The charger comprises a main body and cooling fins provided on the main body, The control device is characterized in that, when the charger is not operating and the temperature of the drive unit is below a predetermined temperature, it sends the coolant to the bypass path, and when the charger is not operating and the temperature of the drive unit is above the predetermined temperature, it sends the coolant to the charger and then to the drive unit.

[0008] Electric vehicles (EVs) and plug-in hybrid vehicles (PHVs) are equipped with chargers that convert household alternating current (AC) power to direct current (DC) voltage to charge high-voltage batteries that store power for driving. When the high-voltage battery is being charged by the charger, i.e., when the charger is operating, it is necessary to cool the charger with coolant to suppress excessive temperature rise. However, when the high-voltage battery is not being charged by the charger, i.e., when the charger is not operating, such as when the vehicle is in motion, the need to cool the charger is low, so it is effective to bypass the circulation of coolant to the charger from the viewpoint of reducing the pump load.

[0009] Incidentally, the inventors of this application have found that, since the charger is located behind the drive unit, by circulating coolant to the charger even when it is not in operation, the charger can also function as a second heat exchanger.

[0010] In other words, with this configuration, when the charger is not operating and the drive unit temperature is below a predetermined temperature, the pump load can be reduced by diverting the circulation of coolant to the charger. On the other hand, when the charger is not operating and the drive unit temperature is above the predetermined temperature, the coolant is deliberately sent to the charger, making the charger function as a second heat exchanger, thereby enhancing the cooling of the drive unit. Thus, this configuration makes it possible to achieve both reduced pump load and improved cooling of the drive unit.

[0011] Preferably, the drive unit comprises a plurality of electrical devices, the temperature detection means is provided in each of the plurality of electrical devices, and the control device is configured to change the order in which the coolant is supplied to each electrical device according to the temperature of each electrical device.

[0012] This configuration enables highly efficient cooling according to the cooling priority of electrical devices.

[0013] Preferably, the drive unit comprises a DC / DC converter and an inverter as electrical devices, and the control device, when the temperature of at least one of the DC / DC converter and the inverter is above a predetermined temperature, first supplies the coolant to the electrical device with the higher temperature.

[0014] With this configuration, the cooling liquid is first supplied to the electrical device with the higher temperature among the DC / DC converter and inverter, thereby effectively cooling the electrical device that requires enhanced cooling.

[0015] The charger comprises a main body and cooling fins provided on the main body. ru.

[0016] According to this configuration, since the charger includes cooling fins, the thermal resistance of the charger is reduced and the heat dissipation amount is increased. Thus, the performance of the charger as the second heat exchanger can be improved.

[0017] Preferably, the main body is disposed inside the vehicle, and the cooling fins protrude outside the vehicle.

[0018] According to this configuration, since the cooling fins protrude outside the vehicle, the performance of the charger as the second heat exchanger can be further improved by heat exchange with the outside air.

[0019] Preferably, the main body is disposed in the trunk floor of the vehicle, the cooling fins extend downward from the main body, and protrude outside the trunk floor.

[0020] According to this configuration, the heat dissipation amount of the charger can be further increased by utilizing the running wind. Thus, the performance of the charger as the second heat exchanger can be effectively improved.

[0021] When the charger is operating, the control device feeds the coolant to the charger.

[0022] According to this configuration, an excessive temperature rise during the operation of the charger can be suppressed.

Effect of the Invention

[0023] As described above, according to the present disclosure, in an electric vehicle cooling system, it is possible to achieve both reduction of the pump load and improvement of the cooling of the drive unit.

Brief Description of the Drawings

[0024] [Figure 1] Schematic diagram showing the main configuration of the vehicle in this embodiment. [Figure 2] Perspective view showing an example of the charger. [Figure 3] Diagram showing an example of the installation state of the charger in FIG. 2. [Figure 4] Schematic side view of the cooling system. [Figure 5] Schematic diagram of the cooling system. [Figure 6] A block diagram showing the relationship between the control device and its main related devices. [Figure 7] A flowchart illustrating an example of a cooling system control method. [Figure 8] Figure 5 is a diagram corresponding to the first state. [Figure 9] Figure 5, which represents the second state. [Figure 10] Figure 5, which represents the third state. [Figure 11] Figure 5 is a diagram corresponding to the fourth state. [Figure 12] A graph showing the temperature difference of the coolant (water) before and after passing through each electrical device during normal driving. [Figure 13] A graph showing the relationship (calculated result) between the amount of heat dissipated by the charger and the temperature difference of the coolant. [Figure 14] A schematic diagram of a conventional cooling system. [Modes for carrying out the invention]

[0025] Embodiments of the present disclosure will be described in detail below with reference to the drawings. The following description of preferred embodiments is illustrative in nature and is not intended to limit the present disclosure, its applications, or its uses in any way.

[0026] <Electric Vehicles> Figure 1 shows Vehicle 1 (electric vehicle). Figure 1 shows a simplified representation of the main components related to the disclosed technology.

[0027] In this specification, direction is based on Vehicle 1. That is, the direction of the length of Vehicle 1 is called the front-rear direction, the front of Vehicle 1 is called "front", and the rear of Vehicle 1 is called "rear".

[0028] Vehicle 1 is a so-called electric vehicle (Battery Electric Vehicle, BEV). Vehicle 1 is equipped with a pair of front wheels 2F, 2F and rear wheels 2R, 2R at the front and rear, respectively. Vehicle 1 moves by rotating the pair of front wheels 2F, 2F using electricity. Inside vehicle 1, there is a motor room 1b located at the front, a passenger compartment 1a located in the center, and a trunk floor 1c located at the rear.

[0029] As shown in Figure 1, this vehicle 1 is equipped with a radiator 2 (heat exchanger), a drive unit 60, a high-voltage battery 6, a low-voltage battery 7, a charger 8, a charging plug 9, and a control device 10, etc. The drive unit 60 is located in the motor room 1b and includes multiple electrical devices such as a drive motor 3, an inverter 4, and a converter 5. The radiator 2 and the control device 10 will be described later in the section on the cooling system 40.

[0030] [Drive motor] The drive motor 3 is an electrical device that generates the driving force necessary for the vehicle 1 to move. The drive shaft of the drive motor 3 is connected to a pair of front wheels 2F, 2F via a reduction gear, clutch, drive shaft, etc. (not shown). The drive motor 3 is a permanent magnet type synchronous motor whose drive shaft rotates due to three-phase alternating current.

[0031] [High-voltage battery] The high-voltage battery 6 is a large secondary battery that stores power for driving. The high-voltage battery 6 is located in the lower part of the vehicle 1, in the area from the passenger compartment 1a to the trunk floor 1c. The high-voltage battery 6 is a high-voltage DC power source and is configured to store power at a voltage of, for example, 300V or higher. The power to drive the drive motor 3 is supplied by the high-voltage battery 6.

[0032] [Inverter] The inverter 4 is an electrical device that controls power. The inverter 4 is interposed between the drive motor 3 and the high-voltage battery 6 and controls the power supplied from the high-voltage battery 6 to the drive motor 3. In this way, the inverter 4 controls the rotation of the drive motor 3.

[0033] The inverter 4 contains an inverter circuit (not shown) that includes multiple switching elements such as IGBTs and capacitors. By controlling the on / off state of these switching elements, the inverter 4 generates a controlled three-phase alternating current using the DC voltage supplied from the high-voltage battery 6. This alternating current is output to the drive motor 3, causing the drive motor 3 to rotate at the required output.

[0034] Furthermore, the inverter 4 is equipped with an inverter temperature sensor 46 (temperature detection means) that detects the temperature of the inverter 4 and outputs a signal indicating the temperature.

[0035] [Low-voltage battery] The low-voltage battery 7 is a rechargeable battery with a rated voltage of 12V (sometimes 24V) connected to a low-voltage power supply system. In other words, the low-voltage power supply system is configured to supply 12V DC power.

[0036] The devices installed in vehicle 1, including common electrical components such as headlights and audio systems, as well as the inverter 4, converter 5, control device 10, and the electric pump 41 (pump) described later, are connected to a low-voltage power supply system. These devices operate using the power supplied from this system.

[0037] [converter] Converter 5 is an electrical device that converts DC power to DC power of a different voltage (a so-called DC / DC converter). Converter 5 is connected to a high-voltage battery 6, as well as to a low-voltage power supply system including a low-voltage battery 7.

[0038] Inside the converter 5 is a step-down circuit (not shown) that includes multiple switching elements such as IGBTs, capacitors, and coils. By controlling the on / off state of these switching elements, the converter 5 steps down the high-voltage power from the high-voltage battery 6 and outputs it to the low-voltage power supply system 15.

[0039] In other words, the converter 5 uses the power from the high-voltage battery 6 to charge the low-voltage battery 7 or to directly supply power to various electrical devices mounted on the vehicle 1.

[0040] Furthermore, the converter 5 is equipped with a converter temperature sensor 45 (temperature detection means) that detects the temperature of the converter 5 and outputs a signal indicating the temperature.

[0041] [Charging path and charger for high-voltage batteries] To charge the high-voltage battery 6, the vehicle 1 is equipped with a charging plug 9, a charger 8, etc. As shown in Figure 1, the charging plug 9 is located at the rear of the vehicle 1. The charger 8 is located at the rear of the vehicle 1, specifically below the trunk floor 1c, so as to be near the charging plug 9.

[0042] Although not shown in the diagram, this vehicle 1 is equipped with two charging paths: a fast charging path and a standard charging path. Charging using the fast charging path (fast charging) is faster than charging using the standard charging path (standard charging). The charging plug 9 includes two types of plugs corresponding to the fast charging path and the standard charging path, namely a high-voltage plug and a low-voltage plug.

[0043] The rapid charging path is a path that directly charges the high-voltage battery 6 using an external power source with a voltage equal to or higher than that of the high-voltage battery 6, i.e., a high-voltage DC supplied from a specific power source such as a charging station. The rapid charging path consists of a high-voltage plug on the charging plug 9 and a cable connecting the high-voltage plug and the high-voltage battery 6. By connecting the connector of the specific power source to the high-voltage plug, the high-voltage battery 6 can be charged directly.

[0044] On the other hand, the normal charging path is a path that charges indirectly using an external power source with a lower voltage than the high-voltage battery 6, that is, a low-voltage AC supplied from a normal commercial power source such as 100V or 200V. The normal charging path consists of a low-voltage plug for the charging plug 9, a charger 8, and cables connecting these to the high-voltage battery 6.

[0045] By connecting the commercial power connector to the low-voltage plug, the high-voltage battery 6 can be charged indirectly. In the normal charging path, the charger 8 converts the AC of the commercial power supply to DC and also boosts the low voltage of the commercial power supply. Specifically, the charger 8 is equipped with a boost / conversion circuit that includes multiple switching elements such as IGBTs, capacitors, and coils. The charger 8 converts the input AC to DC and boosts its voltage by controlling the on / off state of these switching elements.

[0046] Figure 2 shows an example of the charger 8 of this embodiment. As shown in Figure 2, the charger 8 comprises a main body 81 and cooling fins 83 provided on the bottom surface 82 of the main body 81.

[0047] As will be explained in more detail later, the addition of cooling fins 83 to the charger 8 reduces the thermal resistance of the charger 8 and increases the amount of heat dissipated. This improves the performance of the charger 8 as a second radiator in the cooling system 40, which will be explained later.

[0048] The cooling fins 83 only need to be provided on the outer surface of the main body 81, and may be provided on an outer surface other than the bottom surface 82, in addition to the bottom surface 82, or in place of the bottom surface 82.

[0049] Figure 3 shows an example of the installation state of the charger 8 shown in Figure 2. As shown in Figure 3, the trunk floor 1c of the vehicle 1 is partitioned by a trunk board 1d, and comprises a trunk room 1e above the trunk board 1d and a pan 1f below the trunk board 1d. For example, the charger 8 can be positioned such that the main body 81 of the charger 8 is placed in the pan 1f of the trunk floor 1c, and the cooling fins 83 extend downward from the main body 81 and protrude outside the trunk floor 1c.

[0050] Because the cooling fins 83 protrude outside the vehicle, the performance of the charger 8 as a second radiator can be further improved through heat exchange with the outside air. In particular, as shown in Figure 3, if the cooling fins 83 protrude from the pan 1f to the underside of the vehicle 1, the airflow during driving can be utilized, thereby effectively improving the performance of the charger 8 as a second radiator.

[0051] As shown in Figure 1, the charger 8 is equipped with a charger temperature sensor 47 that detects the temperature of the charger 8 and outputs a signal indicating its temperature.

[0052] <Cooling System> When the drive motor 3 is operating, current flows through the coil located inside it. This causes the coil to generate heat due to its electrical resistance, and the internal temperature of the drive motor 3 rises. If the internal temperature rises excessively, it may lead to a decrease in motor performance and failure. Therefore, the drive motor 3 requires cooling.

[0053] Furthermore, since the inverter 4, converter 5, and charger 8 perform so-called switching control during operation, their electrical circuits generate heat due to electrical resistance. If the temperature of the electrical circuits becomes excessively high, there is a risk of damage to the circuits. Therefore, each of the inverter 4, converter 5, and charger 8 requires cooling, especially during operation.

[0054] As shown in Figures 4 and 5, this vehicle 1 is equipped with a so-called cooling system 40 (electric vehicle cooling system) to cool each of these electrical devices that require cooling.

[0055] The cooling system 40 consists of a radiator 2 (heat exchanger), an electric pump 41, a coolant circuit 42, and a deaeration tank 43 (see Figure 4) for removing air contained in the coolant. Note that the deaeration tank 43 is omitted from Figure 5 and Figures 8 to 11 described later for simplicity.

[0056] The cooling system 40 cools each electrical device by circulating and supplying the coolant cooled by the radiator 2 to each of the electrical devices.

[0057] In this specification, the upstream side in the direction of coolant delivery in the cooling system 40 may be referred to as the "upstream side," and the downstream side in the direction of coolant delivery may be referred to as the "downstream side."

[0058] [Radiator] As shown in Figures 4 and 5, the radiator 2 is installed on the coolant circuit 42 and is a device for cooling the coolant.

[0059] As shown in Figure 1, the radiator 2 is positioned at the front of the vehicle 1 so as to extend in the width direction of the vehicle. The radiator 2 faces the front grille 11 that covers the front surface of the vehicle 1. When the vehicle 1 is in motion, outside air flows into the motor room 1b through the front grille 11. When the vehicle 1 is stopped, outside air flows into the motor room 1b through the front grille 11 by the drive of a fan (not shown). The radiator 2 cools the coolant by exchanging heat with the outside air.

[0060] [Electric pump] The electric pump 41 is a device for supplying coolant to the coolant circuit 42, and, without being limited, is specifically a non-positive displacement pump. The electric pump 41 is connected via piping to the upstream side of the radiator 2 on the coolant circuit 42. When the electric pump 41 is operating, the coolant circulates through the coolant circuit 42 in the direction indicated by the dashed arrow f in Figure 5.

[0061] The electric pump 41 operates according to the control of the control device 10. The control device 10 has a command value (e.g., duty cycle) for the output to the reference electric pump 41 that is pre-set to match the cooling system 40. The electric pump 41 is controlled to operate at the reference output when the cooling system 40 is in use (so-called on / off control).

[0062] [Cooling liquid] The coolant used in the cooling system 40 is not particularly limited, and a known coolant commonly used in automobile cooling systems can be used. Specifically, for example, an antifreeze containing water, ethylene glycol, etc., which does not freeze even at sub-zero temperatures such as -30°C can be used as the coolant. This antifreeze has a higher viscosity than water, and its viscosity increases as the temperature decreases.

[0063] [Cooling fluid circuit] As shown in Figure 4, the coolant circuit 42 consists of piping and other components for circulating coolant, which are connected to the drive unit 60 and the charger 8.

[0064] As shown in Figure 5, the coolant circuit 42 includes a first path 42a, a second path 42b, a third path 42c, a fourth path 42d, a fifth path 42e, a sixth path 42f (bypass path), and switching valves A, B, and C for switching these paths.

[0065] Figure 5 shows the state when vehicle 1 is stopped and the high-voltage battery 6 is not being charged, i.e., the cooling system 40 is not in use. That is, the electric pump 41 is not operating, and the switching valves A, B, and C are all in the OFF position.

[0066] The first path 42a contains the drive motor 3, electric pump 41, radiator 2, etc. The coolant that has passed through the drive motor 3 is configured to be sent to the radiator 2 via the electric pump 41.

[0067] The downstream side of the first path 42a branches into the second path 42b and the sixth path 42f, and a switching valve A is provided at the branching point. Switching valve A selects either the second path 42b or the sixth path 42f as the path connected to the downstream end of the first path 42a. Specifically, when switching valve A is ON, the coolant is supplied to the second path 42b and not to the sixth path 42f (see Figures 8, 10, and 11). On the other hand, when switching valve A is OFF, the coolant is supplied to the sixth path 42f and not to the second path 42b (see Figure 9).

[0068] The charger 8 is located on the second path 42b. As described above, the radiator 2 and the drive unit 60 are located at the front of the vehicle 1. In contrast, the charger 8 is located behind the drive unit 60, i.e., at the rear of the vehicle 1. Therefore, as shown in Figure 4, the second path 42b is formed by a pair of pipes that extend long in the front-rear direction along the underside of the passenger compartment 1a of the vehicle 1.

[0069] The downstream side of the second path 42b branches into the third path 42c and the fourth path 42d, and a switching valve B is provided at the branching point. The switching valve B selects either the third path 42c or the fourth path 42d as the path connected to the downstream end of the second path 42b. Specifically, when the switching valve B is ON, the coolant is supplied to the third path 42c (see Figures 8 and 10). On the other hand, when the switching valve B is OFF, the coolant is supplied to the fourth path 42d (see Figure 11).

[0070] Converter 5 and inverter 4 are located on the third path 42c and the fourth path 42d, respectively. That is, when the switching valve B is ON, the coolant that has passed through the charger 8 is sent to the converter 5. When the switching valve B is OFF, the coolant that has passed through the charger 8 is sent to the inverter 4.

[0071] Although the fifth path 42e is also connected to the branching point where the switching valve B is installed, coolant is not directly supplied from the second path 42b to the fifth path 42e. When switching valve B is ON, the fourth path 42d and the fifth path 42e are connected. When switching valve B is OFF, the third path 42c and the fifth path 42e are connected.

[0072] The downstream ends of the third path 42c and the fourth path 42d are connected to the upstream end of the first path 42a, and a switching valve C is provided at the confluence point. The switching valve C causes either the third path 42c or the fourth path 42d to become a path connected to the upstream end of the first path 42a. Specifically, when the switching valve C is ON, a path is formed through which coolant flows from the third path 42c to the first path 42a (see Figures 8 and 11). On the other hand, when the switching valve C is OFF, a path is formed through which coolant flows from the fourth path 42d to the first path 42a (see Figures 9 and 10).

[0073] Although the fifth path 42e is also connected to the junction where the switching valve C is installed, coolant is not directly supplied from the fifth path 42e to the first path 42a. When the switching valve C is ON, the fourth path 42d and the fifth path 42e are connected. When the switching valve C is OFF, the third path 42c and the fifth path 42e are connected.

[0074] As will be explained in more detail later, when switching valves A, B, and C are set to ON, ON, and OFF respectively, the second path 42b, the third path 42c, the fifth path 42e, the fourth path 42d, and the first path 42a are connected in this order (see the third state D3, which will be explained later, in Figure 10). In this path, the charger 8, the converter 5, the inverter 4, and the drive motor 3 are connected in series in this order. In this path, the coolant is supplied to the drive motor 3 by passing through the charger 8, the converter 5, and the inverter 4 in this order.

[0075] Furthermore, when switching valves A, B, and C are set to ON, OFF, and ON respectively, the second path 42b, the fourth path 42d, the fifth path 42e, the third path 42c, and the first path 42a are connected in this order (see the fourth state D4 described later, Figure 11). In this path, the charger 8, inverter 4, converter 5, and drive motor 3 are connected in series in this order. In this path, the coolant is supplied to the drive motor 3 by passing through the charger 8, inverter 4, and converter 5 in this order.

[0076] Thus, in the cooling system 40 according to this embodiment, the liquid supply order of the inverter 4 and converter 5 can be changed by switching the switching valves A, B, and C.

[0077] The sixth route 42f is a route that bypasses the charger 8, and its downstream side is connected to the middle of the third route 42c. Although not shown in the diagram, the sixth route 42f can be piping located inside the motor room 1b.

[0078] The correspondence between the ON / OFF states of the switching valves A, B, and C and the paths described above (for example, the ON state of switching valve A corresponds to the connection state of the first path 42a and the second path 42b) is for convenience only and is not limited to this correspondence.

[0079] The coolant circuit 42 is also equipped with a coolant temperature sensor 44 for detecting the temperature of the coolant. The coolant temperature sensor 44 is located, for example, downstream of the drive motor 3 where the temperature of the circulating coolant is highest.

[0080] [Control device] As shown in Figure 1, the control device 10 is mounted on the vehicle 1. The control device 10 consists of hardware such as a CPU, RAM, and ROM, and software such as a control program implemented on the hardware. The control device 10 comprehensively controls the movement of the vehicle 1.

[0081] As shown in Figure 6, the control device 10 is functionally configured with a pump control unit 10a that controls the electric pump 41, a switching valve control unit 10b that controls the switching valves A, B, and C, and a motor control unit 10c that controls the operation of the drive motor 3 by the inverter 4. Signals are input to the control device 10 from various sensors such as the converter temperature sensor 45, inverter temperature sensor 46, charger temperature sensor 47, and coolant temperature sensor 44. These temperature sensors may also indirectly detect temperature from current or the like.

[0082] The motor control unit 10c of the control device 10 controls the inverter 4 based on signals input from the converter temperature sensor 45, etc. For example, the control device 10 determines a temperature abnormality in the converter 5, etc., based on signals input from the converter temperature sensor 45, etc. As a result, when the control device 10 determines that there is a temperature abnormality, the control device 10 performs control to limit the output of the drive motor 3.

[0083] The pump control unit 10a and the switching valve control unit 10b of the control device 10 control the electric pump 41 and switching valves A, B, C, etc., based on signals input from the converter temperature sensor 45, inverter temperature sensor 46, charger temperature sensor 47, and coolant temperature sensor 44, etc., and control the circulation of coolant to the coolant circuit 42. In other words, the control device 10 ensures that the cooling system 40 functions properly so that each electrical device to be cooled, such as the inverter 4, converter 5, drive motor 3, and charger 8, does not experience temperature abnormalities.

[0084] <Cooling system control method> When vehicle 1 is stopped, at least the drive motor 3 and inverter 4 do not operate. Charging of the high-voltage battery 6 is performed when vehicle 1 is stopped. When charging the high-voltage battery 6 using commercial power, the charger 8 operates. The converter 5 may operate even when the vehicle is stopped, depending on the power status of the low-voltage power supply system 15.

[0085] On the other hand, when vehicle 1 is in operation, the drive motor 3 and inverter 4 operate. The converter 5 operates according to the power status of the low-voltage power supply system 15, such as when the capacity of the low-voltage battery 7 decreases. The charger 8 does not operate when vehicle 1 is in operation.

[0086] In other words, in this vehicle 1, the electrical equipment operates both when the vehicle is stopped and when it is in operation, so the cooling system 40 is also used accordingly. Specifically, when the vehicle 1 is in operation, the drive motor 3, inverter 4, and converter 5 operate and generate heat, so the electric pump 41 is operated to cool them. When the vehicle 1 is stopped, the charger 8 and converter 5 operate and generate heat as needed, so the electric pump 41 is operated to cool them.

[0087] Figure 7 shows an example of the control flow of the cooling system 40.

[0088] First, it is determined whether the charger 8 is in use or not (step S1).

[0089] When the charger 8 is in operation, that is, when the vehicle 1 is stopped and the high-voltage battery 6 is being charged via the normal charging path, as shown in Figures 7 and 8, the switching valves A, B, and C are all set to the ON state (first state D1) so that the coolant flows to the second path 42b. In this way, the coolant is supplied to the charger 8 to cool it and suppress an excessive temperature rise in the charger 8. Furthermore, by setting the switching valves B and C to the ON state, the coolant that has passed through the charger 8 is supplied to the converter 5. In this way, the converter 5 can also be cooled.

[0090] In this case, although the drive motor 3 is not operating, it generates the most heat among the electrical devices included in the drive unit 60, so the cooling system 40 is configured to always supply coolant to it when it is operating. The coolant circuit 42 could be configured so that the coolant bypasses the drive motor 3 when it is not operating, but the configuration of this embodiment is preferred from the viewpoint of reducing the number of branches in the coolant circuit 42.

[0091] As shown in Figure 7, when the charger 8 is not in use, the temperature of the inverter 4 T in step S2 I / V and the temperature T of converter 5 DCDC Obtain it.

[0092] Then, in step S3, the temperature T of the inverter 4 I / V and the temperature T of converter 5 DCDC Determine whether at least one of the following is above a predetermined temperature.

[0093] For example, during normal driving, or when the vehicle is stopped and the high-voltage battery 6 is being charged via the rapid charging path, the temperature T of the inverter 4 I / V and the temperature T of converter 5 DCDC All of these will be below the predetermined temperature. In this case, as shown in Figures 7 and 9, switching valves A and C are set to OFF and switching valve B is set to ON (second state D2). In this way, the coolant is sent to the sixth path 42f and prevented from flowing into the second path 42b. This shortens the path length of the coolant circuit 42 and reduces the load on the electric pump 41.

[0094] The sixth path 42f is connected to the upstream side of the converter 5 on the coolant circuit 42, and the coolant supplied to the sixth path 42f is supplied to the converter 5. Subsequently, the coolant is supplied to the inverter 4 via switching valve C and switching valve B, and then to the drive motor 3 via switching valve C. For example, during normal operation, the amount of heat that can be generated by these electrical devices is lowest in the converter 5, followed by the inverter 4, and then the drive motor 3. In principle, it is desirable to supply the coolant in the order that the electrical device that generates less heat is placed upstream of the coolant circuit 42, so that each electrical device can be cooled efficiently. However, since the difference in the amount of heat generated by the converter 5 and the inverter 4 during normal operation is not large, the order in which the coolant is supplied to the two may be reversed.

[0095] As shown in Figure 7, in step S3, the temperature T of the inverter 4 I / V and the temperature T of converter 5 DCDCWhen at least one of them is determined to be at a predetermined temperature or higher, the process proceeds to step S4. Then, the temperature T of the inverter 4 I / V is determined whether it is higher than the temperature T of the converter 5 DCDC .

[0096] For example, when the usage amount of the low-voltage power supply system increases and the power of the high-voltage battery 6 is voltage-converted and used, etc., the heat generation amount of the converter 5 increases. Then, the temperature T of the converter 5 DCDC is higher than the temperature T of the inverter 4 I / V , or rather, the temperature T of the inverter 4 I / V is lower than the temperature T of the converter 5 DCDC . Then, it becomes necessary to strengthen the cooling of the converter 5

[0097] In this case, in the present embodiment, as shown in FIGS. 7 and 10, the switching valves A and B are turned ON and the switching valve C is turned OFF (third state D3). Thereby, the coolant is sent through the switching valve A to the second path 42b, that is, to the charger 8. Then, it is sent to the converter 5 through the switching valve B, sent to the inverter 4 through the switching valves C and B, and then sent to the drive motor 3 through the switching valve C again

[0098] Here, the inventors of the present application have found that since the charger 8 is arranged behind the drive unit, by circulating the coolant to the charger 8 even when not charging, the charger 8 can also play a role as a second radiator

[0099] That is, in this configuration, by deliberately sending the coolant to the charger 8 and then to the converter 5, the cooling of the converter 5 can be strengthened

[0100] In addition, in this configuration, the charger 8 is provided with cooling fins 83 that project outward below the vehicle 1. Thereby, the temperature of the coolant can be further reduced by using the running wind of the vehicle 1, which can contribute to the cooling of the converter 5

[0101] Next, for example, during high torque or prolonged regeneration, the amount of heat generated by the inverter 4 increases. As a result, the temperature T of the inverter 4 increases. I / V The temperature T of converter 5 DCDC Beyond T DCDC It will be higher than that. This means that the cooling of inverter 4 will need to be strengthened.

[0102] In this embodiment, as shown in Figures 7 and 11, switching valves A and C are set to ON and switching valve B is set to OFF (fourth state D4). As a result, the coolant is sent through switching valve A to the second path 42b, i.e., to the charger 8. Then, it is sent through switching valve B to the inverter 4, then through switching valves C and B to the converter 5, and finally through switching valve C again to the drive motor 3.

[0103] As a result, the coolant, whose temperature has been further reduced by passing through the charger 8, is sent to the inverter 4, thereby effectively enhancing the cooling of the inverter 4.

[0104] Thus, according to the cooling system 40 of this embodiment, when the temperature of the inverter 4 and converter 5 is below a predetermined temperature when the charger 8 is not operating, the load on the electric pump 41 can be reduced by diverting the circulation of coolant to the charger 8. On the other hand, when the temperature of at least one of the inverter 4 and converter 5 is above a predetermined temperature when the charger 8 is not operating, the coolant is deliberately sent to the charger 8, so to speak, making the charger 8 function as a second radiator, thereby enhancing the cooling of the inverter 4 or converter 5. In this way, this configuration makes it possible to achieve both reduced pump load and improved cooling of the drive unit.

[0105] Furthermore, in the third state D3 and the fourth state D4, after supplying coolant to the charger 8, the coolant is supplied first to the electrical device with the higher temperature. Specifically, in the third state D3, of the inverter 4 and converter 5, the coolant is supplied to the converter 5, which has the higher temperature, before being supplied to the inverter 4. In the fourth state D4, conversely, the coolant is supplied to the inverter 4, which has the higher temperature, before being supplied to the converter 5. Thus, in the cooling system 40 according to this embodiment, the order in which the coolant is supplied to each electrical device can be changed according to the temperature of the inverter 4 and the converter 5. This enables highly efficient cooling according to the cooling priority of the electrical devices.

[0106] Normally, coolant is supplied to electrical devices in order from those generating less heat to those generating more. However, the heat generated by the inverter 4 and converter 5 increases only during normal operation. Furthermore, the internal structures of both are similar, and even when their temperatures are above a predetermined temperature, the temperature difference between them is rarely extremely large. Therefore, in this configuration, coolant is supplied first to the electrical device with the higher temperature, effectively cooling the electrical device that requires enhanced cooling.

[0107] <Example of experiment> Specifically, I will explain the results of our verification of the coolant temperature in conventional cooling systems.

[0108] In the conventional cooling system 400 shown in Figure 14, the coolant supplied to the coolant circuit 142 by the electric pump 141 passes through the radiator 102, and then sequentially through the converter 105, inverter 104, charger 108, and drive motor 103. The layout of each electrical device inside the vehicle is the same as in Figure 1.

[0109] Figure 12 shows the temperature difference of the coolant (water) before and after passing each electrical device during normal driving at 100 km / h for the cooling system 400. In Figure 12, the data shown by the solid line are measured values, and the data shown by the dashed line are calculated values. During normal driving, the converter 105, inverter 104, and drive motor 103 are in operation, while the charger 108 is inoperable.

[0110] As shown in Figure 12, the temperature of the coolant that has passed through the converter 105, inverter 104, and drive motor 103 has all increased. On the other hand, the temperature of the coolant that has passed through the radiator 102 has decreased. Furthermore, it was found that the temperature of the coolant that has passed through the charger 108 (without cooling fins) has also decreased. In other words, this result indicates that the charger 108, when not in use, is dissipating heat through natural convection, and can be used as a second radiator.

[0111] Based on the results in Figure 12, and taking the ambient temperature into consideration, the heat dissipation and thermal resistance of the charger 108 were calculated to be approximately 100W and approximately 4.8K / W, respectively.

[0112] If the charger 108 is equipped with cooling fins similar to those shown in Figure 2, the thermal resistance of the charger 108 is expected to decrease to approximately 2.4 K / W. Consequently, the heat dissipation of the charger 108 is expected to increase to approximately 550 W.

[0113] Figure 13 shows the relationship (calculated result) between the heat dissipation of the charger 108 and the temperature difference of the coolant. As shown in Figure 13, when the heat dissipation of the charger 108 increases from approximately 100W to approximately 550W, the temperature of the coolant that has passed through the charger 108 is predicted to decrease by nearly 1°C. This calculation result is shown by a dashed line in Figure 12.

[0114] Furthermore, as shown in Figure 3, for example, if the cooling fins are positioned to protrude outside the vehicle, the heat dissipation of the charger 108 will increase further, and it can be predicted that the function of the charger 108 as a second radiator will be further improved.

[0115] <Other Embodiments> Other embodiments relating to this disclosure will be described below. In the description of these embodiments, the same reference numerals will be used for parts that are the same as those in the above embodiments, and detailed descriptions will be omitted.

[0116] The installation location of the charger 8 is not limited to the trunk floor 1c, as long as it is located behind the drive unit 60.

[0117] The charger 8 does not need to have cooling fins 83. Also, if the charger 8 does have cooling fins 83, the cooling fins 83 do not need to protrude outside the vehicle.

[0118] Furthermore, from the viewpoint of improving the function of the charger 8 as a second radiator, if the charger 8 is equipped with cooling fins 83, it is more desirable that the charger 8 be configured such that its main body 81 is located inside the vehicle 1 and the cooling fins 83 protrude outside the vehicle, regardless of the installation location of the charger 8.

[0119] To increase the heat dissipation of the charger 8, a fan capable of blowing air onto the charger 8 may be provided.

[0120] The order in which the coolant is supplied by the drive motor 3 and the electric pump 41 may be reversed. That is, the coolant circuit 42 may be configured so that the coolant passes through the drive motor 3 after passing through the electric pump 41.

[0121] In the above embodiment, the drive motor 3 is not equipped with a temperature sensor. However, a temperature sensor may be provided, for example, on the casing of the drive motor 3, so that the temperature of the casing surface of the drive motor 3 is detected as the temperature of the drive motor 3.

[0122] When the vehicle is stopped and the high-voltage battery 6 is being charged via the rapid charging path, the cooling system 40 may be kept in a non-operational state (Figure 5).

[0123] Vehicle 1 may be, for example, a Range Extender EV. In that case, vehicle 1 includes a range extender unit in which the engine, generator, and converter are integrated. The engine is an engine for generating electricity. The generator generates electricity using the power of the engine. The converter is connected to the generator and the high-voltage battery 6, and converts the alternating current generated by the generator into direct current to charge the high-voltage battery 6. If vehicle 1 is a range extender EV, the generator and converter included in the range extender unit may also be placed on the coolant circuit 42 as electrical devices included in the drive unit 60. [Industrial applicability]

[0124] This disclosure is extremely useful because it can provide a cooling system for electric vehicles that can achieve both reduced pump load and improved cooling of the drive unit. [Explanation of symbols]

[0125] 1 vehicle (electric vehicle) 1c Trunk floor 2. Radiator (heat exchanger) 3. Drive motor (electrical device) 4. Inverter (Electrical device) 5. Converters (Electrical devices, DC / DC converters) 6 High-voltage battery 8 charger 81 Main Unit 83 Cooling Fins 10 Control device 40 Cooling System 41 Electric pump (pump) 42 Coolant circuit 42f Route 6 (Bypass Route) 45 Converter temperature sensor (temperature detection means) 46. ​​Inverter temperature sensor (temperature detection means) 60 Drive Unit

Claims

1. A cooling system for an electric vehicle comprising a drive unit positioned in front of the vehicle and a charger positioned behind the drive unit, A coolant circuit connected to the drive unit and the charger, and having a bypass path that goes around the charger, A pump provided on the aforementioned coolant circuit for supplying coolant to the coolant circuit, A heat exchanger provided on the aforementioned coolant circuit for cooling the coolant, The drive unit is provided with a temperature detection means for detecting the temperature of the drive unit, The system includes a control device that controls the circulation of the coolant to the coolant circuit based on the temperature of the drive unit detected by the temperature detection means, The charger comprises a main body and cooling fins provided on the main body, The control device is When the charger is not operating and the temperature of the drive unit is below a predetermined temperature, the coolant is sent to the bypass path. When the charger is not in operation and the temperature of the drive unit is above a predetermined temperature, the coolant is supplied to the charger and then to the drive unit. A cooling system for electric vehicles characterized by the following features.

2. In claim 1, The aforementioned drive unit is equipped with a plurality of electrical devices, The temperature detection means is provided in each of the plurality of electrical devices, The control device is configured to change the order in which the coolant is supplied to each electrical device according to the temperature of each electrical device. A cooling system for electric vehicles characterized by the following features.

3. In claim 2, The aforementioned drive unit includes a DC / DC converter and an inverter as its electrical devices. The control device, when the temperature of at least one of the DC / DC converter and the inverter is above a predetermined temperature, first supplies the coolant to the electrical device with the higher temperature. A cooling system for electric vehicles characterized by the following features.

4. In claim 1 or claim 2, The main unit is located inside the vehicle, The cooling fins protrude outside the vehicle. A cooling system for electric vehicles characterized by the following features.

5. In claim 4, The main body is located inside the trunk floor of the vehicle. The cooling fins extend downward from the main body and protrude outside the trunk floor. A cooling system for electric vehicles characterized by the following features.

6. In claim 1 or claim 2, The control device, when the charger is operating, supplies the coolant to the charger. A cooling system for electric vehicles characterized by the following features.

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